How to maintain the same pixel appearance, when rendering a exported image sequence
Imagine an image of 140x139 (this one : )
If you import in blender with images as plane addon, with emission or shadeless shader
And set your render output to the same resolution and framerate 
And add an orthographic camera above to the center of your image, with orthographic view
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You can adjust the size by zooming a lot in a corner from the camera view (Numpad 0) and adjust the Orthographic Scale.
Set color management to standard to don't have filmic transformation
And sampling to 1 to avoid anti aliasing.

The resulting image shouldn't be different.(I checked on photoshop : )
However, if you want to move the plane (rotate, or distort) the pixel will change as the raster sample the same pixels to in the same location. It will rasterize the image depending on the new transform, some pixels may stay the same, but some others will change.
Example of a distorted image :